Disclosed are methods for preparing phenolic branched chain fatty acids or alkyl esters thereof, involving subjecting in a pressurized container (a) at least one phenolic compound, (b) unsaturated fatty acids having 6 to 25 carbon atoms, alkyl esters thereof, or mixtures thereof, and (c) H-ferrierite zeolite catalyst in the presence of distilled water or alcohol and a nitrogen atmosphere at a temperature of about 100° C. to about 400° C. and a pressure of about 10 to about 1000 psi, and isolating saturated phenolic branched chain fatty acids or alkyl esters thereof or mixtures thereof; wherein the ratio of said at least one phenolic compound: said unsaturated fatty acids or alkyl esters thereof is about 100 to about 1, wherein the yield of said saturated phenolic branched chain fatty acids is greater than about 70 wt %, and wherein there is at least one phenolic on the fatty acid alkyl chain. Also disclosed are methods for killing microorganisms on or in an object, involving contacting said object with an effective microorganisms killing amount of a composition comprising phenolic branched chain fatty acids or alkyl esters thereof, and optionally a carrier; the phenolic branched chain fatty acids or alkyl esters thereof may be produced by the methods described herein.
Vegetable oils and animal fats are excellent feedstocks for the production of biobased products which are environmentally benign; however, the carbon-carbon double bonds in the fatty acids of these lipids are not stable at elevated temperatures and this can limit their applications. Therefore, for many uses they must undergo subsequent reactions in order to have such desirable properties as superior lubricity and good thermal and oxidative stability while maintaining high flash and fire points, high viscosity index numbers, and good biodegradability. In addition, although numerous biobased fluids are commercially available, each displaying unique properties that are suited in applications such as cosmetics, biobased paints, biodegradable lubricants and polymers, metal working fluids, biodiesel, and more (Tullo, A. H., Chemical and Engineering News, 88 (15): 16-19 (2010); Shen, L., et al., Biofuels, Bioprod. Bioref., 25-40 (2010); Frisby, K., The Navy's Environmental Magazine, Winter 2006, pages 48-50; Mittelbach, M., and C. Remschmidt, Biodiesel the comprehensive handbook, Boersedruck Ges.m.b.H, Vienna, Austria (2004)), there is significant interest in developing new chemical classes from these fats and oils. Thus, there is a continuing need to increase the diversity and versatility of biobased industrial fluids by the chemical modification of these fats and oils.
One useful group of fatty acid (FA) derivatives is the branched chain fatty acids (BCFA) in which one or more linear and/or aromatic carbons are attached to the linear carbon chain of the FA. Among the advantages of BCFA relative to their unmodified FA counterparts in industrial applications are their lower melting and cloud points. Recent advances in the processing of agricultural feedstocks have included the development of new paths for the production of BCFA. Most of these processes use homogeneous (e.g., soluble) catalysts or stoichiometric amounts of reagents for functionalization of fatty acids. Rangarajan et al. reported the synthesis of hydroxyl fatty acids, commercially important products in themselves, via epoxidation of unsaturated linear-chain fatty acids (ULC-FAs) followed by ring-opening of the epoxidized products (Rangarajan, B., et al., J. Am. Oil Chem. Soc., 72: 1161-1169 (1995)). The hydroxyl groups were subsequently esterified by alkyl, acyl, or aryl groups to generate hydroxyl ester branched-chain fatty acids. Carboxylic acid esters of these FA may have interesting properties, such as low-temperature fluidity and lubricity. The simultaneous homogeneous acid catalyzed addition of alcohols to epoxidized soybean oil and transesterification of the fatty acyl ester bond to yield hydroxyl ester products with substantially improved low temperature performance has been reported (Hwang, H. S., and S. Z. Erhan, J. Am. Oil Chem. Soc., 78: 1179-1184 (2001); Hwang, H. S., J. Am. Oil Chem. Soc., 80: 811-815 (2003)). Biermann et al. reported the Lewis acid catalyzed additions of alkyl groups (i.e., isopropyl, cyclohexyl, t-butyl and others) to ULC-FAs to give hydro-alkylation products (Biermann, U., and J. O. Metzger, Eur. J. Lipid Sci. Technol., 110: 805-811 (2008)). Ionescu et al. reported alkylation of vegetable oils with phenol in the presence of triflic acid and tetrafluoroboric acid catalysts. This method gave a mixture of phenol alkylated polymerized oil (30-60%), phenyl esters (<10%), and unreacted oil (30%) (Ionescu, M., and Z. S. Petrovic, J. Serb. Chem. Soc., 76: 591-606 (2011)).
Heterogeneous (i.e., solid phase) catalytic approaches have also been used for upgrading fats and oils. Roe et al. reported the first example of heterogeneously catalyzed branching of ULC-FA by condensing a phenolic compound with oleic acid (OLA) with an ion-exchange resin, leading to an approximately 30% yield of phenyl-branched-fatty acids (Roe, E. T., et al., J. Am. Oil Chem. Soc., 36: 656-659 (1959)) which were reported to have antioxidant properties. Kohashi et al. reported the addition of aromatic compounds to fatty acid double bonds by heterogeneous acid clay catalysts to give aryl-branched-chain fatty acids (ABC-FAs) (Kohashi, H., J. Am. Oil Chem. Soc., 61: 1048-1051 (1984)). In 1995, Alink reported the catalytic arylation of OLA with aromatic hydrocarbons (i.e., xylenes) in the presence of clay catalysts (i.e., Montmorillonite K10, Clarion 470 and 550) to give xylylstearic acid products with up to 90% yields (Alink, B. A. O., U.S. Pat. No. 5,440,059 (1995); U.S. Pat. No. 5,840,942 (1998)). Unfortunately, the clay catalysts used by Alink cannot be recycled and reused. In 1991, Alink disclosed an arylation of OLA with aromatics (i.e., toluene, xylenes, and phenol) using highly acidic perfluorinated resins grafted with sulfonic acid (Alink, B. A. O., U.S. Pat. No. 5,034,161 (1991)); however, although these resin catalysts gave relatively high yields (80%) of the ABC-FA products, the amount of catalysts needed were equal to that of the OLA used in the reaction. Zhang et al. reported the arylation and isomerization of OLA with aromatic species (i.e., toluene) in the presence of zeolite (i.e., Cu-Beta and H-Beta) and anion modified zirconia catalysts to give a mixture of SBC-FAs (saturated branched chained-FAs (alkyl substituted)) and ABC-FAs (Zhang, Z., WO 2005/014766 A2 (2005), U.S. Patent Application Publication 2007/0015928); however, the simultaneous production of both products (i.e., SBC-FAs (alkyl substituted) and ABC-FAs)) led to only moderate yield of ABC-FA products. More recently, Zhang reported the use of another catalytic system, anion modified sulfated and tungstated zirconia catalysts, to obtain a maximum conversion of OLA of 78.4 wt % after 6 h at 250° C. (Zhang, S., Catal. Lett., 127: 33-38 (2009)); however, this system still concurrently produced both products (i.e., SBC-FAs (alkyl substituted) and ABC-FAs)) which led to only moderate yield of ABC-FA products of 38.2 wt %.
Thus, it is still important to develop new synthetic approaches to improve the production of aryl-branched-chain fatty acids while minimizing the production of other byproducts such as dimer and lactones. We have developed new synthetic approaches and have found that the resulting aryl-branched-chain fatty acids, particularly the phenolic branched-chain fatty acids (PBC-FAs), can be used against foodborne diseases.
Foodborne diseases are a public health concern affecting a large number of people and resulting in significant economic cost in the United States and worldwide. It is estimated by the Centers for Disease Control and Prevention (CDC) that foodborne illnesses in the United States cause about 48 million sicknesses, 128,000 hospitalizations, and 3,000 deaths each year (Scallan, E., et al., Emerging Infectious Diseases, 17(1): 7-15 (2011)). Three recent studies provided cost-of-foodborne-illness estimates ranging from $14.1 billion to $152 billion (Hoffmann, S., et al., J. Food Protect., 75(7): 1291-1302 (2012); Hoffmann, S., and T. D. Anekwe, Making sense of recent cost-of-foodborne-illness estimates, EIB-118, U.S. Department of Agriculture, Economic Research Service, September 2013; Scharff, R., Health-related costs from foodborne illness in the United States, Produce Safety Project, Georgetown University, Washington, D C, 2010; Scharff, R., J. Food Protect., 75(1): 123-31 (2012)). Bacteria that have been frequently associated with the outbreaks of foodborne diseases include both Gram-negative and Gram-positive bacteria such as Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, Clostridium perfringens, and Campylobacter spp. (CDC, Centers for Disease Control and Prevention, Food Safety, 2011).
One of the major challenges for ensuring microbial food safety is the limited effectiveness of common sanitizers used by the industry which are capable of only achieving 1-2 log reduction of common pathogens in many foods (Beuchat, L. R., et al., J. Food Protect., 67: 1238-1242 (2004)). There are many possible reasons for this limited ability to inactivate pathogens in food. One of the reasons is that bacterial cells are able to protect themselves, with the bacterial cell membrane acting as a diffusion barrier between the cytoplasm and the extracellular medium. The integrity of this membrane is crucial for the survival of bacteria as the disruption of the cell membrane would result in cell injury and death. The cell membrane consists of a phospholipid bilayer with embedded proteins. Membranes are usually impermeable for most hydrophilic compounds (ions), a property which is essential for controlling the composition of the cytoplasm, although small hydrophilic compounds can be transported into cells through various protein channels such as porins (Konings, W. N., et al., Antonie van Leeuwenhoek, 81: 61-72 (2002); Galdiero, S., et al., Curr. Protein Pept. Sci., 13: 843-854 (2012)). In addition, there is a concern about the use of chlorine (a common sanitizer) by the food industry and other industries due to the potential environmental and health risks associated with the formation of potentially harmful chlorine by-products (Olmez, H., and U. Kretzschmar, LWT-Food Sci. Technol., 42, 686-693 (2009)). Chlorine reacts with organic matter and forms potential carcinogenic products such as trichloromethane (Richardson, S. D., et al., Water Air Soil Pollut., 123: 95-102 (2000); Hua, G., and D. A. Reckhow, Water Res., 41: 1667-78 (2007)). For this reason, chlorine is banned for use on certain food products in many EU nations. Furthermore, there is an increasing demand for novel environmentally friendly antimicrobials from renewable resources produced by clean and sustainable technology. With increasing environmental awareness and emphasis on sustainability and renewability, natural or bio-based active compounds are becoming more attractive.
Phenolics and medium-chain fatty acids are naturally occurring compounds commonly found in plants and are by-products of food processing. A few of these compounds, such as cinnamaldehyde, thymol and carvacrol, have antimicrobial properties (Burt, S., Intl. J. Food Microbiol., 94(3): 223-53 (2004); Di Pasqua, R., et al., J. Agric. Food Chem., 55: 4863-4870 (2007); Yun, J., et al., J. Food Sci., 78: M458-M364 (2013)). However, these antimicrobial compounds are volatile and possess unpleasant characteristic odors which prevent their use in the food industry. Medium chain fatty acids are also known to have antimicrobial proprieties; however, their antimicrobial ability is relatively low (Kabara J. J., and D. L. Marshall, Medium chain fatty acids and esters, IN: P. M. Davidson, J. N. Sofos, A. L. Branen, (Eds.), Antimicrobials in Foods, 3rd ed., Taylor and Francis, Roca Raton, Fla. (2005), pp. 327-360).
We found that our synthetically prepared phenolic branched-fatty acids (PBC-FAs) mixtures surprisingly had antimicrobial properties against microorganisms (e.g., Gram-positive and Gram-negative bacteria).